Grade Three Music Theory - Lesson 6: Time Signatures

Click here to read this lesson with US terminology e.g. "quarter note" instead of "crotchet".

Quick Revision

A time signature is made up of two numbers, one written above the other. It’s written only at the beginning of a piece of music, or within the music if the time signature changes in the middle of a piece. (It’s not written on every new line, unlike the clef and key signature).

The top number tells you how many beats (not notes) to count in each bar. The bottom number tells you what type of note to count.

Simple Time Signatures

Up till now you have only learnt about simple time signatures. (Perhaps you didn’t think they were very “simple” though!)

A simple time signature is one where:

the top number in the time signature is 2, 3 or 4

the main beat is divided into two

the main beat is not a dotted note

the bottom number of the time signature tells you what type of note is used for the main beat

.

For example, in 4/4 the main beat is a crotchet. If we want to divide the crotchet, we split it into two quavers:

In 2/2, the main beat is a minim. We can split each one into two crotchets:

And in 3/8, the main beat is a quaver. We can split each one into two semiquavers:

Compound Time Signatures

Compound time signatures are new for grade three theory. A compound time signature is one where:

the top number is 6, 9 or 12

the main beat is divided into three

the main beat is always a dotted note

the bottom number shows you the division of the beat, not the main beat.

Here are the three compound time signatures you need to know for grade three theory:

6/8

The bottom number 8 tells us to count quavers, the top number tells us there should be 6 in a bar. But, the main beat is not quavers – because that would give us six beats in the bar. (There are always, 2, 3 or 4 beats per bar, or an irregular number which doesn't divide into 2, 3 or 4, such as 7).

We need to work out what note value is equal to three of the notes in the time signature: what are 3 quavers worth?

Three quavers = one dotted crotchet.

Each bar has two dotted crotchet beats.

In fact, the main beat in any /8 time is the dotted crotchet.

The quavers should always (whatever the time signature) be beamed to make complete beats whenever possible:

This grouping is wrong, because the quavers are grouped to make three beats, instead of two. (This grouping would be fine for 3/4 time, which has three beats per bar).

9/8

There are 9 quavers per bar.

Each group of three quavers makes one main beat, which is worth a dotted crotchet.

There are three dotted crotchet beats per bar.

Here you can see the dotted crotchet main beats, which are then each sub-divided into three quavers. The quavers are beamed in threes, to make up one complete beat each.

12/8

There are 12 quavers per bar.

Each group of three quavers makes one main beat, which is worth a dotted crotchet.

There are four dotted crotchet beats per bar. The quavers are beamed to make it easy to see that there are four beats per bar.

Remember! An undotted note is always split into two. A dotted note is always split into three.

Duple, Triple and Quadruple Time

All the time signatures that we’ve learnt so far can be described as duple, triple or quadruple.

These words refer to the number of main beats per bar.

In simple time, it’s very easy to work out – just look at the top number.

2=duple, 3=triple and 4=quadruple.

2/2 and 2/4 are duple time

3/2, 3/4 and 3/8 are triple time

4/2 and 4/4 are quadruple time

In compound time, you need to count the number of main beats, or you can divide the top number by 3.

6/8 is duple time (2 dotted crotchets per bar)

9/8 is triple time (3 dotted crotchets per bar)

12/8 is quadruple time (4 dotted crotchets per bar)

Here’s all that information summarised in a table:

(Top Number)

Duple

Triple

Quadruple

Simple

2

3

4

Compound

6

9

12

(For a complete table of time signatures including examples, please see the time signature chart in our reference section).

Triplets

Triplets are introduced at Grade 3 in the Trinity syllabus but at grade 2 for ABRSM. Please see TRIPLETSfor more information.